Control apparatus for checking and controlling sequential machine operations



Filed 001;.

E. J. HUNKELER ET AL CONTROL APPARATUS FOR CHECKING AND CONTROLLING l4 SheetsSheet 1 F l L db .3

I I V [f2 4/- [Z IO INVENTORB FIGJ.

ERNST J-HUNKELER, 3 ROBERT R-wMsboRP ikxwww 14M ATTORNEYS July 21, 1970 I E, HUNKELER ET AL I 3,521,524

.CONTROL APPARATUS FOR CHECKING AND CONTROLLING SEQUENTIAL MACHINE OPERATIONS Filed 00".- l, 1968 l4 Sheets-Sheet 2 INVENTORS ERNST JMWKELE T ROBERT A-WAASDORP ATTORNEYS vwmwu wmm July 21, 1970 HUNKELER ET AL 3,521,524

CONTROL APPARATUS FOR CHECKING AND CONTROLLING SEQUENTIAL MACHINE OPERATIONS Filed Oct. 1. 1968 no.7.v W

14 Sheets-Sheet 4 July 21, 1970 E. J. HUNKELER ETAL "3,521,524

CONTROL APPARATUS FOR CHECKING AND CONTROLLING SEQUENTIAL MACHINE OPERATIONS v 7 Filed Oct. 1, 1968 i4 Sheets-Sheet 5 INVENTORS T HUNKE LER ROBERTA. WARS amp ATTORNEY) July, 0 E. J. HUNKELER E AL 3,

7 V CONTROL APPARATUS FOR CHECKING AND CONTROLLING SEQUENTIAL MACHINE OPERATIONS Filed Oct. 1, 1968 l4 Sheets-Sheet 6 204 F/GJIQ /82 INVENTORS ERNST. J- HUNKELER. 8 ROBERT-A. wAkSDoRP ATTORNEYS y 21, 1970 E. J. HUNKELER ET AL 3,

'CONTROL APPARATUS FOR CHECKING AND CONTROLLING SEQUENTIAL MACHINE QPERATIONS l4 Sheets-Sheet 9 37/ FIGJZ j Filed Oct. 1. 1968,

3/4 500 RQE I r 1 338 l F1 INVENTORS ERNST T-HUNRELEK 6k ROBERT AWARSDORP Law ATTORNEY July 21, 1970 E NK ET AL 3,521,524

' CONTROL APPARATUS FOR 0 NG AND CONTROLLING SEQUENTIAL MACHINE OPERATIONS Filed Oct. 1, 1968 l4 She e'ts-Sheet l0 FIG. 19.

INVENTORS 1 ROBERT A was new ERNST S. HUNKELER,

3,521,524 CONTROL APPARATUS FOR CHECKING AND CONTROLLING:

Ju y 21, 1970 E. J. HUNKELER E AL SEQUENTIAL MACHINE OPERATIONS l4 Sheets-Sheet 11 Filed Oct. 1, 196 8 INVENTORS ERNST MWNRELE d ROBERT A. WARSDORP AL,@,,L

y 1, 1970 E. J. HUNKELER ET AL 3,521,524

CONTROL APPARATUS FOR CHECKING AND CONTROLLING SEQUENTIAL MACHINE OPERATIONS Filed Oct 1 1968 14 Sheets-Sheet 12 J uly 21, 1970 E. J. HUNIKELERA ET AL 5 5 CONTROL APPARATUS FOR CHECKING AND CONTROLLING I SEQUENTIAL MACHINE OPERATIONS Filed 001;, 1. 1968 14 Sheets-Sheet 14 INVENTOR$ ERNST IMNKELER Rosem- A. waasooev fzmzw wgv jw ATTORNEY 5 United States Patent Oflice 3,521,524 Patented July 21, 1970 US. Cl. 90-1 20 Claims ABSTRACT OF THE DISCLOSURE A work loader and transfer device for handling and moving gear blanks and gear pieces from one station to another in a gear cutting apparatus is disclosed. The work loader and transfer device is constructed'to operate between at least two cutting or working positions of a machine and includes means for being lifted and lowered as well as rotated back and forth about a vertical axis of rotation. Work holding devices are positioned on the ends of arms associated 'with the work loader and transfer device, and more than one type of work holding device may be associated with a single work loader and transfer means. Each work holding device includes a centering cup means for contacting a gear piece and for centering the same relative to the work loader and transfer device, and jaw members are provided for affecting a tight grip of the workpiece. Means may be provided for rotating or indexing the workpiece relative to the loader and transfer device so that the workpiece is properly oriented for a cutting operation. A control system is provided for checking and controlling a sequence of operations of a machine, and the control system may be combined with the Work loader and transfer device to effect its sequential operations. The control system includes means for taking air read-outs of various functions of a machine to detect a failure of any given function in a sequence, and the control system includes means for shutting down automatic operation of a machine if such a failure occurs. In addition, a checking device is provided on a bevel gear cutting machine to determine proper stock division and seating of a workpiece after it has been transferred to a work station. The checking device may be included in the control system so that improper positioning of a workpiece Will result in a shutdown of handling operations for a gear cutting machine. Also, a method for handling Work blanks and workpieces between two or more stations of gear cutting apparatus is described.

BACKGROUND AND BRIEF DESCRIPTION OF INVENTION This invention relates to improvements in apparatus and systems for loading, handling, and transferring work pieces from one station to another relative to machines which can perform a series of sequential operations on the workpieces. In particular, one part of the invention is concerned with a work loader and transfer arrangement for bevel gear cutting machines of the type where two or more work stations are provided for roughing or finishing work blanks and workpieces. The work loader arrangement includes a device which can load workpieces into and out of work stations of a gear cutting machine, and the device includes means for transferring the same workpieces from one station to the next in machines which involve more than one cutting operation. The work loading and transferring arrangement of this invention provides for a novel method of processing workpieces from a source and through a series of cutting operations.

Another part of the invention involves a novel control system for checking the completion of each operation involved in a sequence of operations of a machine. The control system has special utility for work loader and transfer devices of the type which will be described for bevel gear cutting machines, but the control system is also useful for any other machine which must perform a series of operations in a sequence which requires that each operation be fully completed before a subsequent operation of the series can be started. The invention also provides for a proper orientation of workpieces relative to a work station of a machine, and a checking device is provided for determining whether proper orientation has taken place. The checking device may be included in the control system so that a detection of improper orientation of the workpiece will stop subsequent operations of the machine before any damage can result.

Generally, it is known in this art to provide for some means of transferring gear blanks and gear pieces from one station to another in gear cutting apparatus. Typical prior art arrangements for handling work in such machines is disclosed in Pats. 2,773,426; 2,782,689; 3,169,- 446; 3,229,585; and 3,354,782. However, for one reason or another, such work handling systems have not become accepted in the industry of spiral bevel and hypoid pinions to any great extent, and the present invention is concerned with solving problems involved in handling workpieces of a shape and size typically encountered in bevel gear cutting operations. Because of the irregular shape of a bevel gear blank and because of a need for very precise placement of such a blank relative to a gear cutting machine, it has been difficult to provide an arrangement which will automatically load and unload such pieces into and out of a gear cutting machine. The problems of handling and placement are compounded even more where more than one gear cutting machine is involved, and the present invention directs itself to improvements which permit a reliable and precise handling of such work'- pieces in high speed gear cutting machines which may include more than one cutting station. The types of machines contemplated by the present invention are being prepared for marketing by Gleason Works under a general development of new machines, and these particular machines are concerned with automatically cutting hypoid pinions, at high speeds and with great precision, for use in automotive drive trains. A number of separate patent applications are being filed contemporaneously with this application to cover various features of machines included in this overall development on the part of Gleason Works, and reference is made to the separate patent applications for descriptions of other improvements associated with such machines.

In addition to improving the handling and transferring of workpieces in gear cutting machines, the present invention provides a novel control system which is useful for checking and controlling a sequence of operations for any machine in which a step of operation must be fully completed before a subsequent step can be started. The control system represents an improvement over prior arrangements which require a great number of electrical switching devices and sensors for checking and controlling a complex sequence of movements inasmuch as it requires only a single fluid pressure switch to sense the completion of each step of a machine operation. This arrangement substantially improves the reliability of a control system by eliminating the problems of switch failure and main tenance associated with devices which involve a great number of switching and detecting mechanisms. Basically, the control system of this invention provides a series of passageways leading to various elements involved in the operation of a machine, and the passageways are situated so that completion of a given operation functions to block an outlet of a given passageway. A single conduit communicating with a source of air under pressure can be placed into communication with selected passageways in sequence by a distributor system provided in the control system, and a pressure sensitive switch in the supply conduit detects the presence or absence of air pressure in the conduit. Detection of a certain level of air pressure maintains continued operation of a control drum associated with dictating the operations of the machine, but a failure to reach a certain level of pressure results in a shutdown of automatic operations until any error in mach ne operation can be completed or corrected. The control drum associated with the control system may comprise a plurality of dams stacked on a common axis of rotation so as to individually dictate control movements to various operations of a machine in accordance with rotation of the drum in which the cams are carried. The air read-out system can be operatively associated with means for rotating the cam drum so that a failure of any single operation of the machine can be detected to stop further rotation of the drum as well as further machine operations which would normally be dictated thereby.

The combination of a work loader and transferring device with the novel control system of this invention provides for a completely automatic method of transferring workpieces from station-to-station in gear cutting machinery involving more than one work station. The work loader and transferring device can be completely controlled and checked in its operation by the control system of this invention so that the proper placement and orientation of each workpiece is detected in each transfer operation. It is very important not only that gear blanks and gear pieces be properly placed in work spindles where they can be cut, but also that they be oriented very precisely so that a single tooth profile can be cut more than once and at more than one work station. For example, after a blank has been rough cut, it is necessary to provide additional cutting operations which finish the profile of the roughed teeth and grooves on the gear blank. Finish cutting may be accomplished by two machines in accordance with the present invention by cutting one side of each tooth groove at one work station, and then, cutting an opposite side of each tooth groove at a second work station. Such cutting operations can be carried out 'at high speeds with dual machines of the type contemplated by this invention, but it can be seen that it is necessary to provide a very precise placement and orientation of each workpiece between each cutting station when finish cutting is to be accomplished in the manner,

just described. Thus, it is also important to detect proper orientation, and to stop further operations if necessary, as provided by the work handling and control system arrangements of this invention.

In addition to the work handling and control system arrangements just described, the invention also provides for a checking device which can determine whether proper orientation of a workpiece has actually taken place between work stations, and this device is positioned near a work spindle so as to check the positioning of a workpiece as it is being received into the work spindle for a cutting operation. The checking device includes a projecting element for detecting stock division of the workpiece, and a separate means is provided for taking an air read-out of the seating of the workpiece in the work spindle. Although prior arrangements have been provided for manually, or otherwise, determining stock division of a workpiece (see for example the mechanical arrangement shown in Pat. 2,782,689), the checking device of the present invention provides improvements which permit the checking functions to be included in an air read-out control system of the type included in this invention.

These and other features of the invention will be discussed in greater detail below, and in that discussion reference will be made to the accompanying drawings which are briefly described below.

4 BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a perspective view of a duel bevel gear cutting machine having two cutting stations between which gear blanks can be moved for separate cutting operations, and this figure illustrates a work loader and transfer means, together with a control system for such means, in a machine of this type;

FIG. 2 is a top plan schematic view of a bevel gear cutting arrangement involving a transfer of work between three separate-stations which include two gear cutting stations and one station supplied by a conveyor;

FIG. 3 is a view similar to FIG. 2 showing a work loader arrangement which operates between three stations which include only a single gear cutting station;

FIG. 4 is a top plan view of radially disposed arm structures associated with the loader and transfer means of this invention;

FIG. 5 is an elevational view, partly in cross section, illustrating a turret assembly associated with the work loader and transfer means of this invention;

FIG. 6 is a cross sectional view of the turret assembly of FIG. 5 as seen on line 6- 6 of FIG. 5;

FIG. 7 is an elevational view similar to that shown for FIG. 5 but angularly displaced 90 degrees around the vertical longitudinal axis of the turret assembly;

FIG. 8 is a plan view in partial cross section to illustrate a means for oscillating the turret back and forth around its central longitudinal axis;

FIG. 9 is an elevational cross sectional view of an upper portion of the turret assembly, illustrating details of dash pot structures associated with vertical movements of the loader arms relative to the turret;

FIG. 10 is a top plan view of the base of the loader and transfer device showing air and hydraulic connection associated with the operation of the turret and loader apparatus;

FIG. 11 is a detailed elevational view in partial cross section of a first type of work holding means associated with the loader and transfer means of this invention;

FIG. 12 is a cross sectional view taken on a horizontal plane on line 1212 of FIG. 11, showing a portion only of the structure of FIG. 11;

FIG. 13 is a detailed elevational view similar to FIG. 11 but showing a second type of holding means which may-be used with the loader and transfer means of this invention;

FIG. 14 is a top plan view of a portion of the holding means of FIG. 13, illustrating a manually operated adjustment mechanism associated therewith;

FIG. 15 is a vertical elevational view in partial cross section, similar to FIGS. 11 and 13, showing a third type of holding means which may be used with this invention;

FIG. 16 is a top plan view of a portion of the holding means of FIG. 15, showing an indexing system which provides for automatic stock division when a workpiece is transferred from one station to another;

FIG. 17 is a vertical schematic layout of functional features associated with a control system of this invention;

FIG. 18 is an elevational view in cross section, showing details of structure of a control system in accordance with this invention;

FIG. 19 is an elevational side view of the control systern of this invention;

FIG. 20 is a front elevational view of the same system shown in FIG. 19;

FIG. 21 is a cross sectional view taken in a horizontal plane to show features of the control system on line 21- 21 of FIG. 20;

FIG. 22 is another cross sectional view similar to that shown in FIG. 20 but taken on line 22-22 of FIG. 20;

FIG. 23 is a third cross sectional view of a portion of the control system taken on line 23-23 of FIG. 20;

FIG. 24 shows an example of a sequential pattern of operations which can be controlled by the control system of this invention when utilized in a gear cutting machine of the type shown in FIG. 1 wherein finishing cutting operations are being carried out on gear workpieces;

FIG. 25 is a top plan view of a checking device associated with the machines of this invention for providing an automatic check of stock division and proper seating of a workpiece in a work holding spindle;

FIG. 26 is an elevational view in cross section, as seen on line 2626 of FIG. 25; and

FIG. 27 is an elevational view in partial cross section of a mechanism associated with a conveyor for handling workpieces.

DETAILED DESCRIPTION OF INVENTION Apparatus and method for loading and unloading workpieces into a bevel gear cutting machine and for transferring workpieces between stations As discussed above, one part of the present invention provides for a novel work loader and transfer means which can be used with bevel gear cutting machines. The novel work loader and transfer means may be positioned between two or more work stations associated with a gear cutting machine. For example, it has now become feasible to provide dual cutting machines having two work stations which can carry out cutting operations simultaneously on two separate workpieces. The loader and transfer means of this invention can be positioned between the two work stations so as to move a Work blank into and out of cutting positions in a method which greatly increases the speed of cutting. In a typical installation, the loader and transfer means may include three arm members radially disposed outwardly from a central vertical turret, and the arm members each carry work holders near their terminal ends so that individual workpieces can be gripped by the Work holders and transferred to different work stations. When dual cutting machines are used in combination with the loader and transfer means, it is preferred that a third station be provided as a point (a) from which workpieces can be received from a supply and (b) to which workpieces can be returned after they have undergone two cutting operations at the two separate stations of the machines. Typically, a work blank will be lifted from the source station, which may be included as a part of a conveyor means, and then, the workpiece will be transferred to a first cutting station of one of the gear cutting machines. Simultaneously, a previously cut workpiece is lifted and transferred from the first work station to a second station associated with a second gear cutting machine, and also at the same time, a third workpiece is returned to the source station from the second cutting machine. Thus, there is a simultaneous gripping, lifting, transferring of three separate workpieces to three different stations, and then, all three workpieces are released for whatever operation is to be performed at their respective stations. After each cutting cycle, the work loader and transfer means is oscillated back to a starting position so that it can once again pick up three workpieces and perform the same transfer operation. The conveyor means may include driving means for moving the workpieces toward and away from a pickup and receiving point, and the driving means is controlled to provide a step-wise movement so that the conveyor is stopped when pieces are being picked up from or deposited on the conveyor. In order to handle work blanks and workpieces with great precision, as is required in finish cutting hypoid pinion gears for example, it is necessary to provide work holder means which function not only to grip a workpiece carefully but also to properly orient a workpiece relative to the cutter of any machine that it will be moved to. It has been found that three different types of holding means are required in certain loading and transfer perations for hypoid pinion gear manufacture, and there will be a detailed discussion of each of the three different types in a later part of this specification.

Referring to FIG. 1, a dual gear cutting machine is shown in perspective view in a typical manufacturing set-up for producing hypoid pinion gears. The dual machine includes a first work station 10 and a second work station 12 at which pinion gear pieces can be received in work spindles associated with the work stations. The means for holding workpieces in place at the stations may include well known mechanisms for chucking and dechucking a workpiece as well as means for moving the entire work spindle assembly into a proper position for engagement of cutters 14 with each of the workpieces. Between the two work stations is positioned a work loader and transfer means 16 which functions to automatically load workpieces into and out of each of the work stations 10 and 12 and to transfer workpieces between those stations as well as between the dual gear cutting machine and a conveyor or other source of supply. The loader and transfer means 16 includes a turret assembly 18 which can be lifted and lowered to raise and drop workpieces at the separate stations in accordance with a precise sequence of operations. In addition, the turret assembly 18 can be rotated about its own vertical axis so as to move arm members, generally indicated at 20, back and forth between the work stations. FIG. 1 also illustrates a control system 300 which is a separate part of this invention and which may be utilized in any machine requiring a careful control and sequencing of a series of operations.

FIGS. 2 and 3 illustrate typical layouts for utilizing the loader and transfer means of the present invention between two or more stations. In the FIG. '2 arrangement, two machines A and B are related to one another, as in FIG. 1, to form a dual cutting machine which may comprises two rougher machines, two finisher machines, or a rougher and finisher combination. The machines A and B have work cutting stations 10 and 12 respectively, and the loader and transfer means 16 is positioned to operate between the two stations 10 and 12. In addition, a third station 24 is provided as a point for receiving new work blanks and as a place for returning finished workpieces. The third station 24 may receive work blanks from a conveyor means 26 which advances a new work blank to the station 24 before each transfer cycle. The same conveyor 26 can receive finished pieces which are transferred from station 12 at the end of each cutting cycle to station 24. It can be seen that each of the work stations 10 and 12 correspond to conventional positions for holding work pieces while a cutting operation is performed by rotating cutting means. The work stations are typically in the form of work spindles held in assemblies 28 and 30 which can be moved relative to the cutting means 14. Means for moving the work head assemblies 28 and 30 are not a separate part of this invention, but generally, means are provided for rocking each of the assemblies 28 and 30 from cutting positions, as related to the cutting machines A and B, to work transfer positions which would place the stations 10 and 12 directly beneath work holders carried by separate arms 32 and 34 of the work loader and transfer means. The work loader and transfer means 16 is oscillated back and forth about the vertical axis of its turret 18 so that arm 32 passes only between stations 10 and 12 and arm 34 passes only between stations 12 and 24. The third arm 36 passes only between the conveyor station at 24 and the first work cutting station 10. Thus, the separate arms 32, 34 and 36 can be provided with different types of work holding means having somewhat different structures and functions for handling workpieces at varying stages of completeness.

FIG. 3 is a view similar to FIG. 2 and shows the use of the loader and transfer means of this invention with a single gear cutting machine A. In this arrangement, only a single cutting station 10 is available to each workpiece,

but a dummy, or banking, station 38 may be provided for holding workpieces until they can be advanced to the cutting station 10. After a cutting operation has been completed at 10, the workpiece is moved by the arm 34 to the conveyor 26 to be received and carried away. Thus, even in the case of a single machine operation, the loader and transfer means of this invention provides for an automatic handling of workpieces from a source of supply, through a cutting operation, and to a point where they can be delivered away from the cutting machines.

FIGS. 4 through 8 illustrate details of construction of the work loader and transfer means 16. As shown in FIG. 4, separate arms 32, 34 and 36 are arranged 120 apart about a vertical central axis of th loader, and means are provided for attaching holding means to terminal end portions of the separate arms. Guide elements 39 may be provided on one or more of the arms to align the arms with an upstanding guide pin 41 fixed to a base or frame portion of the machine on which the loader is carried. The guide pin 41 assure a correct alignment of the loader 16 with separate work stations while the loader is being moved up and down to pick up or release workpieces. As seen in FIGS. -7, the turret assembly of the machine includes an outer cylindrical casing 40 which is aflixed to a portion of the frame of a machine with which it is associated. As shown in FIG. 5, the casing 40- includes an integral base portion 42 which can be bolted to any convenient part of a machine base or frame. The casing 40 functions as a support for mechanisms which lift and lower and rotate the loader and transfer means. Concentrically positioned within a bore formed in the casing 40 are a drive shaft 44 and a lifting and lowering shaft 46. The drive shaft 44 functions to rotate the loader arm 20 back and forth about the central vertical axis of the turret 18, and the lifting and lowering shaft 46 includes a piston means to lift and lower the loader and transfer means in response to fluid pressure applied to the piston means. The drive shaft 44 and the lifting and lowering shaft 46 are tubular in construction so that they can be mounted concentrically relative to one another and to the turret tube 40. The drive shaft 44 includes a central bore which is divided into two fluid chambers by a tubular element 48. The tubular element 48 is spaced inwardly from the surface of the central bore of the drive shaft 44 so that hydraulic fluid can be admitted through an inlet 50 into an annular passageway 51 which is formed around the tubular element 48. A separate chamber 52 is defined by a bore through the tubular element 48, and this chamber is sealed from the annular passageway 51 around the element 48. The central chamber 52 receives a supply of hydraulic fluid from a separate source for ultimate use in activating holder means associated with the arms of the loader and transfer means. The flow of hydraulic fluid into the inlet 50 and around the tubular element 48 through passage 51 serves a purpose of lifting the loader and transfer means by an application of fluid pressure into a chamber 54 communicating with the annular passage 51 associated with inlet 50.

Considering the lifting and lowering system for the loader and transfer means, hydraulic fluid is admitted into the inlet 50 and through the passageway 51 for applying a pressure to an upper piston portion of the shaft 46. As shown in FIGS. 5 and 7, fluid which is introduced into the inlet 50 rises upwardly through annular passageway 51 of the turret assembly until it enters the chamber 54. Fluid pressure in the chamber 54 initially acts against a surface 56 which is formed on the lifting and lowering shaft 46, and this applies a lifting force to the shaft 46 and all associated parts as related to the fixed position of the inner drive shaft 44. A separate fluid chamber 58 is provided around the shaft 46 for driving the shaft downwardly with a separate fluid supply which is admitted at 60. When the turret assembly is being lifted, hydraulic fluid is admitted into the inlet 50 and fluid is exhausted from the annular chamber 58 by a reverse flow out of its inlet 60. The reverse takes place when the turret assembly is lowered inasmuch as hydraulic fluid is admitted into the inlet 60 and its associated annular chamber 58 while fluid is allowed to flow out of the chamber 54 and its associated inlet 50. Thus, the inlets 50 and 60 function as both inlets and outlets at different times of a lifting and lowering cycle. The means for admitting hydraulic fluid into either of the inlets 50 or 60 comprises conventional arrangements which include a source of hydraulic fluid, pumping means, and valving means for controlling direction of flow. The means for timing the flow of hydraulic fluid into and out of loader 16 may comprise the control system which will be discussed in a separate part of this specification.

In addition to providing for a lifting and lowering of the loader and transfer means in response to application of hydraulic fluid, means are provided for dampening the lifting and lowering movements when they reach their upper and lower limit positions. For example, when the turret assembly is lifted by an admission of hydraulic fluid into the inlet 50, there would be an abrupt stopping of the turret upon reacting its uppermost position if means were not provided for dampening its upward movement. The means for slowing the upward movement of the lifting and lowering shaft 46 near its upper limit is shown in greater detail in FIG. 9. When the tubular shaft 46 is initially lifted, it is necessary that hydraulic fluid contained within the annular chamber 58 be allowed to escape from that chamber. However, hydraulic fluid can flow out of the chamber 58 only at an upper level of the chamber through a main outlet 62 or an alternate outlet 64. The outlet 62 is unrestricted and allows a free flow of hydraulic fluid out of the annular chamber 58 downwardly through the passageway 61 associated with the inlet 60 of the chamber 58. However, spacer elements in the form of sleeves 66 which can be contained within the annular chamber 58 are carried upwardly with the upward movement of the shaft 46 because the spacer elements 66 rest on an enlarged portion of the shaft 46 at 68. As the shaft 46 reaches its upper limit of travel, the spacer elements 66 block the free-flowing passageway 62, and this forces all remaining fluid in the chamber 58 to escape through the alternate passage 64. The alternate passage includes a restrictor valve 70 therein for restricting the flow of fluid downwardly through the valve and into the passageway 61. The restricting function of the valve 70 is provided by a very small bore 72 which limits the flow of fluid downwardly through the valve body. This restriction of flow of fluid substantially retards the final upward movement of the shaft 46 since hydraulic fluid cannot escape from the chamber 58 rapidly enough to allow continued rapid upward movement of the shaft 46. Thus, by the time the shaft 46 reaches its uppermost position, it has been dampened in its rate of travel by the dampening means just discussed.

When it is desired to lower the turret assembly, hydraulic fluid is admitted into the inlet 60 and its passageway 61 for a pressurized flow into the chamber 58. Inward flow of hydraulic fluid through the passageway 61 initially passes through the restrictor valve 70 in a reverse direction from what was discussed above, and it can be seen that the valve body can be displaced from its seated position for this reverse flow. This allows an easy admission of hydraulic fluid through the passageway 64 and into an uppermost part of the annular chamber 58, to initiate downward movement of the shaft 46. Of course, once the spacer elements have moved downwardly enough to open the passageway 62, the inward flow of fluid can also travel through that passageway. Initial downward movement of the turret assembly is also assisted by the weight of the loader and the arm elements carried by the shafts 46 and by a release of fluid pressure from the annular passageway 51 associated with the inlet 50. However, it is desirable to provide a positive downward displacement of the shaft 46 in order to rapidly and precisely move the transfer and loader means to its lowermost position, and therefore, hydraulic fluid is admitted into the chamber 58 for applying a downward pressure on the enlarged portion 68 of the lifting and lowering shaft 46. When the lifting and lowering shaft 46 approaches its lowermost limit, it is desirable to dampen the final movement of the shaft so as to cushion the lower limit stopping of the loader and transfer means. This dampening function is performed by a dash pot arrangement provided above the chamber 54. As shown in FIGS. and 7,, the chamber 54 is defined in part by a reduced cylindrical end portion 74 of the central drive shaft tube 44. This reduced end portion 74 remains fixed to the drive shaft 44 and does not lift and lower with the movements of the surrounding shaft 46. A further re duced end portion 76 is affixed to the end 74 so that when the lifting and lowering shaft 46 is lifted, the reduced end portion 76 remains at a fixed level. This means that hydraulic fluid which is admitted into the chamber 54 also flows past the reduced end portion 76 and into an upper chamber 78 so as to ultimately apply additional lifting force against the surface 80. Once the shaft 46 is at a sufficiently high level to provide wide clearance between the reduced end portion 76 and a corresponding reduced bore portion of the shaft 46, there is an easy flow of hydraulic fluid upwardly into the chamber 78. As shown in FIGS. 5 and 7, the reduced end portion 76 is tapered slightly so that it is of a smaller diameter at its upper level than it is at a lower level. This arrangement provides a varying restriction of flow of hydraulic fluid out of the upper chamber 78 when the shaft 46 is being moved downwardly. The shaft 46 includes an upper section 82 having a reduced diameter bore for receiving the reduced end portion 76. As the shaft 46 is lowered to its lowermost position, the bore portion of 82 approaches the upper end of the reduced end portion 76. At this point, there is a restriction of flow of hydraulic fluid out of the upper chamber 78 because it must escape past the end portion 76 in order to find its way downwardly into the chamber 54 and ultimately through the annular passageway 51. Thus there is an initial dampening of the downward movement as soon as any part of the portion 82 approaches the reduced end portion 76. However, the dampening effect is increased because of the tapered configuration of the end portion 76, and it can be seen that as more and more of the end portion 76 is received into the bore of portion 82, there is more and more restriction of flow of fluid past the reduced end portion 76. This restriction takes place when the loader and transfer means is near its lower limit position. Thus, there is provided a means for dampening both upper and lower limits of movement for the turret assembly.

As discussed above, the central drive shaft 44 does not raise and lower with the raising and lowering of shaft element 46. The central drive shaft 44 functions only to oscillate the loader and transfer means about a central vertical axis of the turret assembly, and this is accomplished by drive means included in the base of the turret assembly, as shown in greater detail in FIGS. 7 and 8. Rotational movements which are applied to the drive shaft 44 are imparted to the lifting and lowering shaft 46 because the two shafts are keyed together as shown in FIG. 6. This arrangement permits both shafts to be rotated but only the outer shaft 46 can be lifted and lowered. Of course, the outer shaft 46 carries all of the upper assembly elements which include the arms 20 and elements associated with the gripping and handling of workpieces as carried by the arms. All of the upper elements of the loader transfer means are bolted, or otherwise secured, to the shaft 46 by way of a plate member 86. The plate member 86 is lifted and lowered and rotated with all movements of the shaft 46.

Considering the means for rotating the drive shaft 44, reference is made to the details of FIGS. 7 and 8 wherein a rack and pinion drive arrangement is illustrated. A pinion gear 90 is affixed to a lower end of the drive shaft 44 in any well known manner so that rotational movements which are applied to the pinion gear 90 will be imparted to the drive shaft 44. A rack 92 is provided for precisely moving the pinion 90 back and forth about a central vertical axis of the turret assembly. The rack 92 is operated by a fluid pressure system which involves the alternate admission of hydraulic fluid to opposite ends of the rack 92. As shown in the drawings, the rack 92 includes cylindrical end portions 94 and 96 which are fitted within a cylindrical chamber 98 formed within the base assembly of the turret assembly. The cylindrical end portions 94 and 96 function as pistons within the bore 98, and the admission of hydraulic fluid into either of the inlets 100 or 102 will function to drive the rack in one direction or the other, depeding upon which inlet is receiving hydraulic fluid. The control system of this invention may be provided for supplying hydraulic fluid under pressure to the inlets 100 and 102 in an alternating sequence and at desired times, and means for pumping and controlling the direction of flow of hydraulic fluid from a source are well known in this art and do not form a separate part of this invention. In order to provide a dampening of the rack 92 at its two limit positions at opposite ends of the bore 98, the inlets 100 and 102 are of a special configuration to extend into the bore 98 for sufficient distances to be received within small diameter bores 104 and 106 provided in the cylindrical end portions 94 and 96 of the rack assembly. The inlets 100 and 102 are preferably in the form of tapered tubular elements 108 and 110 which provide a dash pot arrangement at each end of the rack 92 when the tapered elements 108 and 110 are received in their respective bores 104 and 106. It can be seen that when the rack is moved one way or the other, it is necessary to admit hydraulic fluid against one of the pistons 94 and 96 While at the same time releasing hydraulic fluid from an opposite end of the rack 92. The release of hydraulic fluid takes place by a reverse flow of fluid through one of the inlets 100 or 102, and as the rack reaches a limit position near the inlet from which hydraulic fluid is being released, there is a restriction of the rate of flow of fluid out of the illlet. For example, as the. rack 92 approaches a lefthand position, as seen in FIG. 8, the tubular element 110 functions as an outlet for a release for hydraulic fluid from the chamber formed at that end of the assembly. However, as the end of the tubular element 110 is received within the bore 106 of the rack, it is necessary for all fluid to escape out of the chamber by travelling around the end of the tubular element and out through its central bore. Since the tubular element has a tapered configuration, flow of fluid around its outside surface becomes more and more restricted as the rack 92 moves closer and closer to the lefthand position. This provides a hydraulic fluid cushion at the end of the piston 96 which prevents an abrupt stopping of the rack at its limit position. The same action takes place when the rack is reversed for a movement to the righthand side of FIG. 8. Also, when movement of the rack is initiated in either direction, there is a slower rate of travel at the beginning of each movement until a tubular element has moved completely away from its associated bore.

The discussion so far has been concerned with means for applying lifting, lowering and oscillating rotational movements to the turret assembly 18 which includes the work handling and transfer arms 20. The arms 20 may comprise specific arms 32, 34 and 36 of the type discussed with reference to FIG. 2, and each of the arms may include a work holding means for gripping a workpiece while it is being transferred from one station to another. Thus, it is necessary to provide mechanisms and systems for operating the work holding means associated with each of the arms which are a part of the work handling and transfer means. Generally, the work holding devices are actuated by hydraulic fluid pressure, and the flow of hydraulic fluid is dictated by the same control system which dictates a flow of fluid into inlets 50 and 60 for applying movements to the turret assembly. However, the admission of hydraulic fluid to the work holder devices associated with each of the arms 32 through 36 takes place through the central bore 52 which passes up through the center of the turret assembly. The central bore 52 may have an inlet 122, and it can be seen that the bore passes up through the turret assembly to a distributor disc 124- carried at the top of the assembly. From there, hydraulic fluid can flow through separate passageways 126 to the separate arms associated with the loader and transfer means. Since the turret assembly moves up and down during normal work handling operations, it is necessary to provide a telescoping feature for the central bore 52 so that hydraulic fluid can be admitted to Work holding devices for all positions of the work transfer and handling means. For this purpose, a separate tubular element 128 is aflixed to the element 86 of the assembly so that it will be carried up and down with vertical movements of the assembly. Sealing gaskets 130 allow vertical movements of the tubular element 128 relative to the drive shaft 44 so that no leakage of hydraulic fluid will take place out of the bore 52. Thus, hydraulic fluid can be admitted to the inlet 122 at prescribed times to effect desired actuations of work holding elements carried near terminal ends of each of the arms associated with the handling and transfer means, and the flow of hydraulic fluid can take place irrespective of the vertical or rotational position of the arms 20.

As mentioned above, each of the arms 20 associated with any given loader and transfer device made in accordance with this invention may include a Work holding device near its terminal end for engaging and gripping a work blank or a workpiece for movement from one station to another. When the work loader and transfer means includes three arms 32, 34 and 36 as shown in FIG. 2, it is possible to provide three different types of work holding devices for each of the three arms when the work handling and transfer device is being used in a dual machine having two work stations and a third station which supplies work blanks and receives finished pieces. The following discussion will describe a basic work holder device with reference to FIGS. 11 and 12, and modifications of the basic work holding device will be described with reference to FIGS. 13 through 16. The FIG. 11 type of work holding device is constructed to handle work blanks which have not been cut at all and which are to be transferred from a conveyor or other supply station to a first cutting station. Also, the basic device of FIG. 11 can be used to move rough cut pinion gear pieces from a conveyor or source of supply to a dummy or bank ing station of the type shown at 38 in FIG. 3. The second type of work holding device is shown in FIG. 13 and includes means to orient a hypoid pinion gear piece which has been previously rough cut. The orienting means comprise one or more pins which can be inserted into a spiral groove of the gear piece so that axial movement of the work holding device relative to the gear piece will result in limited rotation of the gear piece. This type of work holding device is utilized for handling rough cut gear pieces which are to be transferred to a finish cutting station. This transfer may be between a source of supply such as a conveyor and a first finish cutting station or between a dummy station and a single finishing station. The third type of work holding device, as illustrated in FIG. 15, includes means for orienting the workpiece very precisely in its movement from one finish cutting station to a second finish cutting station. This is very important when a hypoid gear piece is being only partly finish cut at one station and completed at a second station because each of the partly finished grooves must be carefully related to the cutter of the second station in order to obtain a precision gear product. The means for orienting 12 the gear piece which are combined with the work holding device of FIG. 15 provide for a carefully controlled and. adjusted orientation of a workpiece between cutting stations.

Referring to FIG. 11, each of the holding devices which are used with the present invention includes a centering cup means and a pair of jaw members 152. The centering cup means is in the form of a metal cup having a downwardly depending annular lip for contacting the tapered surface of a gear piece, and the centering cup means functions to assist in a precise centering of a gear piece relative to the work holding means and to provide a continuous surface against which the workpiece may be tightly gripped. The jaw members 152 function to engage a lower surface or heel 154 of a gear piece and to draw the gear piece into tight engagement with the centering cup means 150. Each of the three forms of work holding devices which will be discussed includes the basic combination of a centering cup means and jaw members which can be moved relative to the centering cup and to a workpiece which is to be gripped in the work holding device. Prior arrangements which utilize only jaw structures do not provide a precise and reliable positioning of a gear piece for a transfer between stations, and further, prior arrangements have not been acceptable to high speed cutting machinery of the type contemplated by this invention because they have not provided for any compensation for the existence of burrs which may develop on the heel portion 154 of a gear piece during normal cutting of the gear piece. The three types of work holding devices which are presented by this invention provide compensation for the existence of burrs while at the same time providing a tight gripping of a workpiece so that rotation of a workpiece can take place While it is being moved from one station to another.

FIG. 11 shows the basic work holding device attached to the end of an arm 36 associated with a work handling and transfer device. The arm 36 may be manufactured from aluminum or an aluminum alloy, and a bore 156 is provided to the arm for allowing vertical movements of the work holding device relative to the arm. A mounting block 158 is aflixed to the arm to carry all elements of the work holding device. The mounting block 158 has a bore formed through it which acts as a cylinder in which a jaw assembly holder 160 can move up and down. Suitable means may be provided for lubricating the cylindrical surface of the jaw assembly holder 160 for its movement within the mounting block 158. The jaw assembly holder 160 includes an enlarged lower portion 162 which carries the centering cup 150. The centering cup 150 may be secured to the jaw assembly holder by bolts 164. The combined jaw assembly holder 160 and centering cup 150 are resiliently mounted within the support block 158 by a number of spring means 166, which space the jaw assembly holder and centering cup downwardly away from the block 158. Opposite ends of the springs 166 are received into recesses in the support block 158 and in the lower portion 162 of the jaw assembly holder, and the spring means 166 are normally compressed to urge the centering cup 150 downwardly relative to the support block 158. The recess which is formed in the support block 158 is in the form of an annular channel which carries an annular ring member 1-67 for rotational movement relative to the annular channel. Bearing means 169 may be provided between the member 167 and the channel to reduce friction. A dowel 171 may be received in an annular ring member 167 so as to rotate the ring member when the jaws are rotated (as in the embodiment of FIGS. 13 and 15) and this prevents springs from being flexed out. The lower limit of travel of the jaw assembly holder 160 and its attached centering cup 150 is set by a top plate 168 aflixed to the upper end of the jaw assembly holder 160. It can be seen that the top plate 168 is of suflicient size to contact an upper surface of the support block 158 when the centering cup is in its lowermost position. A pin 170 may be fixed 

